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For metastable β Ti alloys, it still remains a key challenge to enhance their limited yield strength (YS) while retaining good strain hardenability and ductility. Here we report a new strategy to evade this trade-off dilemma via introducing an uncommon hierarchical structure with the assistance of spinodal structures. The new Ti–11Mo–2V alloy exhibits high YS (693 MPa), high ultimate tensile strength (857 MPa) and large total elongation (31.8 %). Such excellent strength-ductility synergy originates from successive activation of multiple deformation mechanisms, including primary {332}<113> twins, secondary martensite and secondary {112}<111> twins. Importantly, the stress-induced secondary martensite is the desirable α′ martensite rather than the common α'' martensite. Spinodal decomposition in parent β grains is expected to facilitate the unusual hierarchical structure where primary {332}<113> twins ensure high YS while secondary α′ martensite and {112}<111> twins result in excellent strain hardening ability. • The new alloy exhibits high yield strength while retaining large ductility. • An uncommon hierarchical structure, including primary {332}<113> twins and secondary α′ martensite, is created. • The products of SIMT are the unusual α′ martensite due to the assistance of spinodal decomposition. [ABSTRACT FROM AUTHOR]

The evolution of the deformation-induced martensite in the drawn 316L stainless steel and its effect on mechanical performance are examined. Both the yield strength and ultimate tensile strength of the 316L wire reach over 2.3 GPa at a drawing strain of 3.44. The deformation production of the wire during the drawing process is dislocation, twin and finally, deformation-induced α′-martensite. The neighboring misorientation between α′-martensite shows a preferential distribution around 60° due to variant selection limited by a double K–S orientation relationship. This preferential misorientation distribution around ∼60° is stable during the drawing process, and the α′-martensite has been refined to possess an average boundary spacing of ∼50 nm at a strain of 3.44. • The strength of the 316L reached 2340 MPa through cold drawing. • 316L with nanoscale lamellar structures of γ (52 nm) and α′ (53 nm) were prepared. • Misorientation between α′-martensite shows a preferential distribution around 60°. [ABSTRACT FROM AUTHOR]

The highest strength of iron wires has been achieved with 84 nm thick nano-lamellae at ε = 10.35. The lamellar coalescence slows down the tensile strength increases at ε > 8.89 and balances the lamellar thinning at ε = 10.35, with the strength increase rate close to 0. [ABSTRACT FROM AUTHOR]

Excellent strain hardening capability holds the key toward a good strength-ductility combination of high- or medium-entropy alloys (HEAs or MEAs). Generally, metastability engineering and heterostructure are known to be two independent strategies for strain hardening. In this work, a hetero-structured metastable (Fe 57.5 Co 20 Cr 12.5 Ni 5 Mo 3 V 2) 99.8 C 0.2 HEA was prepared in order to incorporate the merits of metastability and heterostructure in one alloy. The annealing microstructure of this alloy consists of heterogeneous face-centered cubic (FCC) grains decorated with various precipitates, including the intergranular submicron M 6 C precipitates, the intragranular nano-sized MC and σ phase. These multiscale precipitates can act as both compositional and dimensional regulators of FCC grains, assisted by tailoring the annealing parameters. The decrease of annealing temperature or duration produces a larger-volume fraction of precipitates and induces carbon-lean FCC grains with a bimodal grain size distribution. Such precipitate-mediated metastability can successively activate the strain-induced FCC→HCP→BCC martensitic transformation (SIMT) over a large strain range. The sequential operation of multiple deformation mechanisms, such as stacking faults, continuous SIMT and precipitation strengthening, ensures an extremely high strain hardening peak (∼4000 MPa) at a high strain level (0.37) and, therefore, achieves a superior synergy of ultimate tensile strength (942 MPa) and total elongation (59%). [ABSTRACT FROM AUTHOR]

Cu–Fe alloy wire with high strength, moderate electrical conductivity and low cost, has a promising application prospect in the electrical industry. In this study, high performance Cu80Fe20 wires were prepared by annealing and drawing at room temperature (RT). Based on the X-ray diffraction and electron microscopy characterization, the influence of microstructural parameters on the mechanical properties and electrical conductivity of the wires were analyzed. The pre-annealing at 500 °C, resulted in the nanoparticles precipitation of Cu in Fe-phase and Fe in Cu-phase, respectively. The drawing deformation greatly improved the strength of wires, while did not result in a significant reduction in the electrical conductivity. Cu nanoprecipitation promoted the refinement of the Fe-phase during deformation, which result in a nano lamellar structure of the Fe-phase with an average boundary spacing as low as 50 nm. Dynamic recovery and recrystallization of the Cu-phase were observed to occur during the drawing at RT with the <112> texture and annealing twinning. The plasticity and electrical conductivity of the Cu-phase were greatly preserved due to the drawing-induced dynamic recovery and recrystallization. Moreover, the strength of the wire was greatly enhanced by the formation of a nano-lamellar structure in the Fe-phase. Hence, the alloy wire at a strain of 3.94 had a high tensile strength of 863 MPa (125% higher than the original strain-free wire), a total elongation of 5%, and the electrical conductivity reached 47 %IACS (only 8 %IACS lower than the original strain-free wire), which shows higher cost properties than other copper alloys. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructural evolution of cementite lamellae in pearlitic steel wires subjected to cold drawing remains elusive, making it difficult to understand the origin of remarkable ductility in cementite. Using high-resolution transmission electron microscopy (HRTEM), the mechanisms underlying the inelastic deformation of cementite in pearlitic steel wires were examined and elucidated. Deformation of cementite in drawing should be included in two mechanisms: (1) Dislocation mechanism: deformation in low strain pearlite should rely on the movement of dislocation. Flat-crystal cementite was broken up into several different orientation cementite particles. (2) Grain rotation mechanism: the deformation mechanism should be by the rotation of cementite particles. Cementite still keeps lamellar shape, but it was divided into a multilayer structure: central nano-crystal and outermost amorphous cementite. [Copyright &y& Elsevier]